Many of us enjoy a summer fishing trip now and then. But tonight, abc's gloria riviera with the catch of a lifetime. With the monster of the deep. Reporter: Meet dr. Zeb hogan. He's been called the fish whisperer, which may not sound like much until you realize we're talking about monster fish. Zeb's a modern-day indiana jones traveling the world tracking down these living leviathans, living fossils zeb fears are going extinct and desperately need to be protected. He invited us to krabi, a remote part of southwestern thailand on the andaman sea, to what he says is the best place in the world to see monster fish for ourselves. And for zeb hogan this is his part-time office. People don't realize that freshwater fish are some of the most endangered animals on the planet. Reporter: Here anglers must follow rules that protect them. Like using barbless hooks that don't hurt them. This fish I'm guessing is at least a 200-pounder, look at the patterns. Reporter: It's an arapaima, the living loch ness. They are big, they are powerful. Reporter: Holy-moly! Next. Amazon redtail catfish. Reporter: Wow! Really nice pattern on its head, bright red tail. Those little moon-shaped pads that you see, those are his teeth. Reporter: Beautiful fish. Yeah, yeah. Reporter: But when he asked if I want to catch one, I'm not sure. Sport fishing an endangered animal? It's so powerful we have to keep trading off. Oh, my god! It's takes three of us to do it but then, zeb hops in the water and my first monster fish is in my net. Whoa! Amazing. It's a giant catfish. Reporter: It's so rare even zeb has seen one in the wild for more than three years. Zeb wishes everyone could do this just once. That was amazing. Gloria riviera, abc news,

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